New Boeing 777X needs more testing, US regulator says

New York

US AIR safety regulators have notified Boeing that the aviation giant's newest widebody plane will require more than two years of additional testing and analysis before it can be certified.

The Federal Aviation Administration (FAA) formally set the timetable for the 777X, saying the jet is "not yet ready" to advance to the next stage of evaluation, according to a letter to the company reviewed Monday by AFP.

Based on inputs from Boeing on the 777X and the test flights conducted so far, certification is "realistically going to be mid to late 2023", said Ian Won, an acting manager in the FAA's aircraft certification service, in the May 13 letter.

Boeing has pushed back the timeframe for the new aircraft several times and previously discussed a "late 2023" schedule for certification. The Seattle Times first reported on the FAA letter which it described as "sternly worded".

The exchange comes as the aerospace giant and FAA face lingering scrutiny on Capitol Hill after the lengthy grounding of the 737 MAX following two fatal crashes.

In the letter, Mr Won pointed to a Dec 8 "uncommanded pitch" event in which the 777X jet performed unexpectedly and said it requires a "root cause" investigation by Boeing.

"We are expecting Boeing to complete comprehensive validation, verification reviews and document the process improvements and lessons learned," he said, calling for a "robust process" to ensure "this is not a systemic issue".

Mr Won also cited a number of other outstanding questions on the new plane.

The company said it was working with the FAA.

"Boeing remains fully focused on safety as our highest priority throughout 777X development" a company spokesperson said.

"As we subject the airplane to a comprehensive test programme to demonstrate its safety and reliability, we are working through a rigorous development process to ensure we meet all applicable requirements."

Shares of Boeing fell 3.4 per cent to US$239.33 in midday trading on Monday.

The decline came amid a pullback in travel stocks due to worries over the Delta variant of the coronavirus.

Meanwhile, Boeing is finalising a set of three safety enhancements to the engines on its popular 737 Next Generation (NG) models to prevent debris from escaping during a failure, according to US regulators.

The FAA outlined the fixes in a letter to the National Transportation Safety Board, dated April 2.

The NTSB had recommended improvements in the engine designs after a chunk of metal flew off a Southwest Airlines engine over Pennsylvania on April 17, 2018, killing a woman who was seated where the metal hit a window.

Once Boeing finalises what are known as service bulletins instructing operators how to strengthen the smooth curved surface at the front of the engine that guides air into the turbine, the FAA plans to mandate them, the agency said in the letter.

The FAA anticipated last April that Boeing would finalise the bulletins by July, though such work is often delayed.

The FAA's letter was earlier reported by Aviation Week.

Several recent episodes in which debris broke loose from the engine inlets have prompted a move to strengthen those areas on 737 NG and some 777s.

"We continue to work with the FAA on potential design changes," Boeing said in an e-mailed statement.

The FAA didn't immediately respond on Monday evening to requests for comment on the April letter. AFP, BLOOMBERG